<!doctype html>
<html lang="zh-CN">
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>多级左侧菜单</title>
    <link rel="stylesheet" href="css/menu.css">
</head>
<body>
<header></header>
<div class="container">
    <nav class="left-nav">
        <ul>
            <li>
                <a class="menu1" href>一级菜单1</a>
            </li>
            <li>
                <a class="menu1" href>一级菜单2</a>
                <ul>
                    <li><a class="menu2" href>二级菜单2-1</a></li>
                    <li><a class="menu2" href>二级菜单2-2</a></li>
                </ul>
            </li>
            <li class="show">
                <a class="menu1" href>一级菜单3</a>
                <ul>
                    <li><a class="menu2" href>二级菜单3-1</a></li>
                    <li class="show">
                        <a class="menu2" href>二级菜单3-2</a>
                        <ul>
                            <li><a class="menu3" href>三级菜单3-2-1</a></li>
                            <li class="active"><a class="menu3" href>三级菜单3-2-2</a></li>
                            <li><a class="menu3" href>三级菜单3-2-3</a></li>
                        </ul>
                    </li>
                    <li><a class="menu2" href>二级菜单3-3</a></li>
                </ul>
            </li>
        </ul>
    </nav>
    <div class="main">main
        <div class="test">内容</div>
    </div>
</div>
<script src="../assets/js/jquery-3.3.1.min.js"></script>
<script src="js/menu.js"></script>
</body>
</html>